Improved thermoelectric performance through double substitution in shandite-type mixed-metal sulphides
Mangelis, P., Vaqueiro, P.
It is advisable to refer to the publisher's version if you intend to cite from this work. See Guidance on citing. To link to this item DOI: 10.1021/acsaem.9b02272 Abstract/SummarySubstitution of tin by indium in shandite-type phases, A3Sn2S2 with mixed Co/Fe occupancy of the A-sites is used to tune the Fermi level within a region of the density of states in which there are sharp, narrow bands of predominantly metal d-character. Materials of general formula Co2.5+xFe0.5-xSn2-yInyS2 (x = 0, 0.167; 0.0 x 0.7) have been prepared by solid-state reaction and the products characterised by powder X-ray diffraction. Electrical transport property data reveal that the progressive depopulation of the upper conduction band as tin is replaced by indium, increases the electrical resistivity and the weakly temperature-dependent (T) becomes more semiconducting in character. Concomitant changes in the negative Seebeck coefficient, the temperature dependence of which becomes increasingly linear, suggests the more highly substituted materials are n-type degenerate semiconductors. The power factors of the substituted phases, while increased, exhibit a weak temperature dependence. The observed reductions in thermal conductivity are principally due to reductions in the charge-carrier contribution on hole doping. A maximum figure-of-merit of (ZT)max = 0.29 is obtained for the composition Co2.667Fe0.333Sn1.6In0.4S2 at 573 K: among the highest values for an n-type sulphide at this temperature.
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